1. Field of the Invention
The present invention relates to a tracking signal processor circuit for obtaining a tracking signal for a video cassette recorder, and to a band-pass filter used in the tracking signal processor circuit.
2. Description of the Related Art
FIG. 5 is an explanatory diagram illustrating a recording process performed in a digital video cam (DVC). A magnetic tape 1 moves around the periphery of a rotary head 2, and the rotary head 2 rotates in a direction which is identical with the direction of movement of the magnetic tape 1. Because the rotary head 2 rotates in a manner such that the rotary head 2 crosses the magnetic tape 1 at an oblique angle, a track oriented at a predetermined oblique angle is formed on the magnetic tape 1. Two heads Lch-Head and Hch-Head are provided on the rotary head 2, and the two heads differ in orientation angle with respect to the magnetic tape 1. These heads are switched by a head switching pulse (HEAD-SW PULSE) so that the heads write alternately.
During such a writing operation, pilot signals having two different frequencies of F1=465 kHz and F2=697.5 kHz are alternately recorded on one of the Hch-side and the Lch-side (in FIG. 5, the Hch-side is shown for the purpose of illustration).
During a replaying process, the recorded magnetic signals are traced by use of the two heads, but if the Lch-HEAD is to be used for tracing and the head position is deviated, signal components recorded on the respective sides of the signal component recorded by the Lch-HEAD, which are recorded by the Hch-HEAD, will leak and become crosstalk components.
As an operation to move the head to the correct point, tracking control of the heads is performed by detecting magnitudes of F1 and F2 signal components recorded on the sides and transmitting, to a servo microcomputer, a point at which the signal components become zero.
In an ATF circuit which serves as a tracking circuit for a DVC, signal components of 465 kHz and 697.5 kHz contained in a replay signal recorded by the two heads (Hch/Lch) on the magnetic tape (TAPE) are respectively extracted by use of band-pass filters 465K-BPF and 697.5K-BPF. The levels of the extracted signal components are compared in a comparator COMP, and the signal of the comparison result is output as the ATF output. The servo microcomputer controls the tracking such that the ATF output becomes 0.
In order to obtain a precise output from the ATF circuit, the transmission center frequencies F0 of the two band-pass filters 465K-BPF and 697.5K-BPF must be set accurately. Normally, there is provided a volume function or the like which can be externally manipulated for this adjustment. This adjustment, however, must be performed for each video camera set during the manufacturing process, and thus, there has been a problem in that this setting process requires significant labor.